The invention relates to an isolating switch of a metalclad installation with an annular earthed metal enclosure filled with a high dielectric strength gas, comprising:
a movable contact in the form of a sliding pin, capable of moving to a closed position engaged with an aligned stationary contact, and to an open position separated from said stationary contact by an isolation gap "d",
a field distribution shield in the form of a fixed cover covering the end of the stationary contact to which it is electrically connected and having a central opening for the movable contact pin to pass through in the closed position of the isolating switch,
a field distribution shield in the form of a cover associated with the movable contact and arranged to cover the end of the movable contact in the open position, and electrically connected to the movable contact.